The present invention generally relates to apparatus and methods for capping containers and, more specifically, to apparatus and methods of ambient atmosphere capping of high speed, in-line containers having contents that can spoil in the presence of air.
In many applications, containers hold contents that are susceptible to spoilage when exposed to air that may become entrapped in the containers when sealed or capped. These contents may, for example, be foodstuffs such as salad dressings. Specifically, air may be entrapped in the headspace between the upper level of the contents and the container opening. This problem exists for both rotating table machines and straight or in-line capping machines. Rotating machines are generally characterized by having rotating tables that convey containers from one table to another, with each table carrying out a specified function. In-line machines, on the other hand, are generally characterized by having a horizontal moving conveyor which carries filled containers at about 250 containers per minute successively past a cap feeding device, a cap applicator device, and a cap sealing device.
In an effort to address the above problem of entrapped air, early filling and sealing/capping processes have been carried out in a vacuum chamber. Since then, sealing and capping methods have been designed to inject an inert gas into the filled or unfilled containers. This is intended to expel air before the container is sealed or capped. In some methods, a vacuum environment has still been needed for evacuating the containers before the inert gas is injected. In at least one method, the container must be evacuated simultaneously with injecting an inert gas. Also, the process of injecting the inert gas has been designed to occur in an inert gas chamber or other inert type of environment.
Like the many methods of capping, the number of different apparatus employed to inject the inert gas and cap the container has been many. In one design shown in U.S. Pat. No. 4,703,609, a nozzle is provided with a plurality of apertures to inject a liquefied gas into a single container to reduce vaporization of the gas and to reduce the amount of liquefied gas falling into spaces between moving containers. Although the containers are to be immediately sealed, the apparatus for doing so is unclearly described.
A gassing rail is disclosed in U.S. Pat. No. 4,827,696 for injecting an inert gas through a plurality of bores and into the headspace of in-line containers. The gassing rail is described as being mounted to the underside of a chute that seats end units or caps onto passing containers. Nevertheless, it is unclear how the gassing rail works in conjunction with the chute, if at all.
Similarly, U.S. Pat. No. 5,916,110 provides a gas-purging rail adjacent to a separate lid placement system. The gas-purging rail extends above the in-line moving containers and includes a plenum having openings to allow an inert gas to flow into the containers. At a line speed of 400 containers per minute, the plenum is approximately 12 feet long. Again, however, it is unclear how the gas-purging rail operates in conjunction with the lid placement system.
Unfortunately, the past methods and apparatus for capping containers in the absence of air in the headspace have disadvantages. The need for expensive vacuum and/or inert gas chambers has made the sealing or capping process expensive. It has also made it slow due to the requirement of moving containers in and out of either a vacuum or inert gas chamber. In fact, even greater time is required when the containers must be stopped to inject an inert gas, conveyed, and then stopped again for applying a cap. Likewise, the apparatus employed has not provided integrated inert gas injection and capping to prevent ambient air from re-entering the containers in an ambient atmosphere. Rather, a non-integrated or discontinuous gas injection and capping has been provided. Also, past apparatus has not provided for increased line speed to consequently reduce manufacturing time and expense.
As can be seen, there is a need for an improved apparatus and method that integrally removes air from the headspace and places caps on in-line moving containers, can be adapted to various sized headspaces, is effective in ambient atmosphere, and allows high in-line speeds of at least about 275 containers per minute.